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Shutemov" , Oleg Nesterov , Song Liu , Andrea Arcangeli , Pavel Tatashin , Allen Pais , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [v4] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged Message-ID: <20200929145519.GF2277@dhcp22.suse.cz> References: <1601338047-18558-1-git-send-email-vijayb@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1601338047-18558-1-git-send-email-vijayb@linux.microsoft.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 28-09-20 17:07:27, Vijay Balakrishna wrote: > When memory is hotplug added or removed the min_free_kbytes must be s@must@should@ > recalculated based on what is expected by khugepaged. Currently > after hotplug, min_free_kbytes will be set to a lower default and higher > default set when THP enabled is lost. This change restores min_free_kbytes > as expected for THP consumers. > > Fixes: f000565adb77 ("thp: set recommended min free kbytes") > > Signed-off-by: Vijay Balakrishna > Cc: stable@vger.kernel.org > Reviewed-by: Pavel Tatashin > Acked-by: Michal Hocko > --- > v3 -> v4 > - made changes to move khugepaged_min_free_kbytes_update into > init_per_zone_wmark_min and rested changes > [suggestion from Michal Hocko] > > [v2 1/2] > - removed symptoms references from changelog > > [v2 2/2] > - addressed following issues Michal Hocko raised: > . nr_free_buffer_pages can oveflow in int on very large machines > . min_free_kbytes can decrease the size theoretically > > v1 -> v2 > -------- > - addressed issue Kirill A. Shutemov raised: > . changes would override min_free_kbytes set by user > > include/linux/khugepaged.h | 5 +++++ > mm/khugepaged.c | 13 +++++++++++-- > mm/page_alloc.c | 3 +++ > 3 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > index bc45ea1efbf7..c941b7377321 100644 > --- a/include/linux/khugepaged.h > +++ b/include/linux/khugepaged.h > @@ -15,6 +15,7 @@ extern int __khugepaged_enter(struct mm_struct *mm); > extern void __khugepaged_exit(struct mm_struct *mm); > extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, > unsigned long vm_flags); > +extern void khugepaged_min_free_kbytes_update(void); > #ifdef CONFIG_SHMEM > extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr); > #else > @@ -85,6 +86,10 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm, > unsigned long addr) > { > } > + > +static inline void khugepaged_min_free_kbytes_update(void) > +{ > +} > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > #endif /* _LINUX_KHUGEPAGED_H */ > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index cfa0dba5fd3b..4f7107476a6f 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -56,6 +56,9 @@ enum scan_result { > #define CREATE_TRACE_POINTS > #include > > +static struct task_struct *khugepaged_thread __read_mostly; > +static DEFINE_MUTEX(khugepaged_mutex); > + > /* default scan 8*512 pte (or vmas) every 30 second */ > static unsigned int khugepaged_pages_to_scan __read_mostly; > static unsigned int khugepaged_pages_collapsed; > @@ -2292,8 +2295,6 @@ static void set_recommended_min_free_kbytes(void) > > int start_stop_khugepaged(void) > { > - static struct task_struct *khugepaged_thread __read_mostly; > - static DEFINE_MUTEX(khugepaged_mutex); > int err = 0; > > mutex_lock(&khugepaged_mutex); > @@ -2320,3 +2321,11 @@ int start_stop_khugepaged(void) > mutex_unlock(&khugepaged_mutex); > return err; > } > + > +void khugepaged_min_free_kbytes_update(void) > +{ > + mutex_lock(&khugepaged_mutex); > + if (khugepaged_enabled() && khugepaged_thread) > + set_recommended_min_free_kbytes(); > + mutex_unlock(&khugepaged_mutex); > +} > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fab5e97dc9ca..ac25d3526fa5 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -69,6 +69,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -7891,6 +7892,8 @@ int __meminit init_per_zone_wmark_min(void) > setup_min_slab_ratio(); > #endif > > + khugepaged_min_free_kbytes_update(); > + > return 0; > } > postcore_initcall(init_per_zone_wmark_min) > -- > 2.28.0 -- Michal Hocko SUSE Labs